Circulation methodologies and systems for hydrocarbon production from oil shale and oil sands and well-rehabilitation and formational pressurization of conventional hydrocarbon systems

ABSTRACT

The extraction of hydrocarbons from two or more wells is enhanced by creating microwave induced permeability zones between the wells, with the zones intersecting or overlapping, so that a fluid pathway is open between the wells and superheated or supercritical fluids and/or selected catalytic compounds flow through the wells and pathways to extract the hydrocarbons and the extracted hydrocarbon flows to a pump for removal from one or more of the wells. For conventional well system, the microwave can rehabilitate stripper wells and increase formational pressure in existing well fields. Porous cavities created by the microwave are suitable for carbon sequestration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and benefits of U.S. Provisional Application No. 61/996,550 filed May 12, 2014, the entire contents of which is hereby expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to equipment and method of use for in-situ control of permeability and viscosity for the extraction of subsurface hydrocarbons with high power microwave (HPM) radiation and enhanced with supercritical or superheated fluids and/or selected catalytic compounds.

BACKGROUND OF THE INVENTION

There are several approaches to produce oil from deep wells, greater than 2000 feet, ranging from conventional ocean and land wells to hydrofracking shale formations in the United States. There are several approaches to produce oil from shallow wells, down to 2000 feet, including mining and surface processing of oil shale and/or sand deposits in the US and Canada. Each production process has shortcomings. Conventional oil wells can be located offshore where natural gas is flared while fuel burning ships and helicopters are needed to service oil platforms. Hydrofracking requires valuable water resources and water treatment facilities to ensure that no discharge of contaminated fracking water reaches the environment. Canada's vast oil sand deposits are currently mined, processed on the surface, and require additional on-site refining before the product can be shipped to the refinery. The environmental impact of oil sand development was described by James Hansen director of the NASA Goddard Institute for Space Studies who wrote in a 2012 New York Times Op Ed, “If Canada proceeds, and we do nothing, it will be game over for the climate.” Carbon costs associated with fertilizer, tractor fuel, coal and natural gas to heat crops to process into biofuels are also significant.

The inventions herein for producing oil from subterranean formations start with a high power microwave (HPM) system disclosed and claimed in U.S. Pat. No. 7,828,057, (the '057 patent) which is incorporated herein as though set forth in full. The High Power Microwave (HPM) System of the '057 patent represents a significant departure from existing technologies for the production of hydrocarbons. The High Power Microwave system is an in-situ technology, meaning that the extraction of oil occurs in the ground, compared with above ground technologies such as e.g., mining and retorting of oil shale and/or oil sand deposits. An antenna is lowered into a well where the focused microwave beam efficiently heats the subsurface water and hydrocarbons for extraction.

There are drawbacks with each of the presently used technologies, such as the mining and retorting, which are overcome by use of the HPM system of the '057 patent.

The High Power Microwave system is a disruptive technology compared with existing hydrocarbon producing technologies. Microwave based hydrocarbon production provides important economic and environmental benefits, such as smaller carbon footprint and valuable water resources that are not required for the extraction of the oil. The extraction of hydrocarbons is further enhanced by coupling the microwave technology of the '057 patent with the circulation of supercritical or superheated fluids and/or selected catalytic compounds.

Oil Shale

Oil in shallow (down to 2000 feet) shale is highly viscous and generally a solid called “kerogen”, and has been essentially untouched by any economical technology and is waiting to be harvested. One of the richest areas of oil shale in the world is the Green River Formation, covering parts of Colorado, Utah and Wyoming. The U.S. Geological Survey estimates that this formation has over 3 trillion barrels of recoverable oil in shale, which is over 150 trillion dollars at a price of $50 per barrel.

There have been numerous attempts over the past 50 years to extract oil from the kerogen in the vast shale deposits in Colorado, Utah, and Wyoming. Early and present day retort processes employ heavy equipment to mine shale with kerogen to be heated in a big oven. The process requires between 3 to 5 barrels of water per barrel of oil produced and involves the disposal of toxic spent ash. This process proposed by Union Oil in the '70s is being adopted by Enefit, an Estonian company, in Utah today. In-situ approaches, such as those used by Shell Oil, AMSO and Exxon, rely on conducting heat through the rock using thermal conduction. The Inventor herein believes conductive heating of rock is physically flawed since rock is an insulator. Shell Oil's process requires 3 to 4 years of heating using outside power sources and a freeze wall surrounding the heating area to protect the environment. A Rand Corporation report stated that Shell would be lucky to achieve a 2:1 energy ratio ($2 of oil for $1 input power cost). AMSO is using a similar conductive heating process using horizontal wells. Electrode failure has plagued the project. And finally, Exxon is using hydrofracturing to place conductive material in the fractures to heat the oil shale.

Major oil companies, e.g., Exxon, Chevron, Shell, Union Oil and Occidental Petroleum, have spent hundreds of millions of dollars during the last thirty years in attempts to change the phase of the oil in oil shale from solid to liquid so that it could be economically recovered. None have been successful to date.

All of the past and presently used processes require more energy and are based on physical processes significantly less efficient than the system of the '057 patent. Also these processes have major environmental disadvantages not found with the system and method of the '057 patent.

The Inventor herein and the Inventors of the claimed invention in the '057 patent have assigned this application and the '057 patent to Qmast LLC, a limited liability company in Colorado. In this application, the environmentally objectionable and costly mining operations presently used would be rendered unnecessary. Furthermore, water is not required to recover the oil. Also, the time consuming, expensive and, thus far, unsuccessful attempt to break down the kerogen by inefficient conductive heat of the shale (rock) could be replaced by Qmast's efficient microwave heating. For comparison purposes, conductive heating by an electrical range uses approximately 6000 watts to heat a cup of water which takes several minutes while dielectric heating of a cup of water by a microwave oven uses less than 1000 watts and takes less than a minute to boil the water?

Oil Sands

There are two technologies currently used to extract oil from the Canadian oil sand deposits. One of the technologies is mining and surface separation processing. The other is known as the SAGD (Steam Assisted Gravity Drainage) process that involves the injection of steam into wells to heat the thick oil to reduce the viscosity, thus, allowing it to flow to production wells. Large quantities of water and wastewater treatment facilities are necessary to handle the contaminated water used in the SAGD process. Conversely, the microwave system efficiently heats in-situ water that strips the bitumen or oil from the oil sands. No outside source of water or large water treatment facilities are required for the microwave technology.

One proposed electrical in-situ approach employs arrays of dipole antennas located in a plastic or other dielectric casing in a formation, such as a tar sand formation. A VHF or UHF power source energizes the antennas and causes radiating fields to be emitted into the deposit. However, at these frequencies, which are below the microwave frequency of the HPM system, the field intensity drops rapidly as distance from the antennas increases because of the electrical properties of the formation. Pore water in the formation is the charge carrier for frequencies below microwaves. Once the pore water is heated to the vaporization point, the circuit is broken and electrical energy cannot be transmitted. The electrode used to transmit electrical energy becomes a heater and inefficient thermal conduction becomes the dominant process.

Rehabilitation

The technology of the '057 patent is also applicable to the extraction of oil from spent conventional wells. These wells are commonly referred to as stripper well—wells that produce less than 10 barrels of oil a day. A common practice to rehabilitate these wells where production has decreased due to the clogging of the formation by viscous substances such as paraffin is to inject hot oil or acid. Hot oil relies on the inefficient conduction of heat while acid treats only a portion of the formation leaving most of the area surrounding the well untouched. The microwave technology of the “057 patent can create a cylinder of permeable rock surrounding a well out to several meters. This permeable cylinder will decrease the pressure gradient resulting in increased production rates that may exceed initial production rates before the well clogged—depending on formational pressures.

Sequestration

As hydrocarbons are extracted by microwave heating, a porous, essentially cylindrical cavern of rock, is left behind that can provide storage or sequestration for CO₂ captured during microwave oil production plus provide storage for other sources of greenhouse gases. For example, in the Green River Formation in Colorado, Utah, and Wyoming, a cement manufacturing facility could be co-located with a microwave oil production facility. The manufacturing of cement is responsible for 6 percent of the world's global greenhouse gas emissions. Fuel produced from microwaving oil shale could power kilns to heat limestone to produce calcium oxide used in the production of cement and the CO₂ emissions may be sequestered in the porous caverns created by the microwave oil production. Not only is the cement produced in an “environmentally friendly” environment but provides an opportunity for carbon credits to offset emissions from the use of the oil produced by the microwave.

A 2005 Intergovernmental Panel on Climate Change (IPCC) report on Carbon Dioxide Capture and Storage states, “deep geological formations at carefully selected sites can store it underground for long periods of time: it is considered likely that 99% or more of the injected CO2 will be retained for 1000 years.” Depleted oil reservoirs are ideal sites for carbon storage. According to the IPCC report, “Mineral carbonation is based on the reaction of CO₂ with metal oxide bearing materials to form insoluble carbonates, with calcium and magnesium being the most attractive metals.” The Green River Formation is a marlstone or calcium carbonate that can fix CO₂ to form minerals that provide sequestration on a geologic time scale.

Effective Way to Extract Oil from Shale

The '057 patent discloses and claims a method and apparatus for extraction of hydrocarbons from subsurface oil shale, oil sands or conventional oil reservoirs. The method claimed in claim 1 of this patent calls for “applying continuous microwave energy at frequencies greater than 2 GHz . . . and launching a narrow phase boundary that reduces the viscosity of the hydrocarbons . . . ”. Claim 3 adds the step of “ . . . applying microwave energy at a power level greater than ½ megawatt to vaporize a portion of the material in the phase boundary . . . ”—specifically the water. Claim 4 calls for the apparatus for extracting hydrocarbons with a continuous source of microwave power equal to or greater than one-half Megawatt and a phase boundary radiating away from the antenna. Claim 8 adds that the source operates above 2 GHz.

A radiating phase boundary capable of reaching radial distances of over 10 m in oil producing formations is created by employing high power microwave energy (500 kilowatts or greater), at frequencies greater than 2 gigahertz, radiating from the antenna to vaporize the water and liquefy the kerogen in the shale. The radiating microwave energy fractures the shale or rock as a result of the expansion of liquid water being vaporized. Once the water is vaporized, it strips the kerogen which is liquefied in the area heated by the microwave energy. Once the lossy water and kerogen are removed, the rock is relatively transparent and the microwave energy migrates outward, passing through the rock until it reaches more water and more kerogen. The launched or migrating phase boundary is expected to reach a distance of over 25 meters from the antenna. This phenomenon is referred to as a migrating phase boundary. The coupling of power into migrating phase boundaries allows for the rapid heating of water and oil in shale and similar oil producing rocks, extensive fracturing of the rock, and production of oil within minutes instead of months or years using other technologies.

Microwave heating of kerogen is caused by orientation polarization, also called dielectric heating. The use of dielectric heating represents a significant departure from previous and existing oil shale production technologies. With dielectric heating the microwave energy couples into molecules that have a dipole structure such as water and to a lessor degree kerogen. Therefore, once the water is removed, the microwave couples directly into the kerogen but not into the rock, as rock is transparent to microwave energy. Superheated vapor from the far field assists in the removal of kerogen by the efficient transfer of thermal energy.

Dielectric heating is different than ionic or conductive heating. Ionic conductivity or heating relies on dissolved ions in the groundwater to conduct electricity through the rock for heating. This is the concept that companies such as Shell Oil and AMSO rely on to heat the rock at lower frequencies, usually in the megahertz range. This works well until groundwater reaches the boiling point (100 degrees C. relative to the pressure), evaporates, and the pathway for the transmission of electricity through the rock is terminated. Above 100 degrees C., the electrode becomes a heater that relies on thermal conduction to heat the rock. The only problem with this approach is that rock is an insulator requiring large amounts of energy to overcome an inefficient physical process.

The fundamental difference that separates the high power microwave approach of the '057 patent from other electromagnetic heating technologies is using the correct frequency to create dielectric heating versus conductive heating as proposed in numerous patents. Following the teachings of Nyfors and Vainikainen (1989), permittivity and losses due to conductivity and dielectric losses as a function of frequency are expressed by the following equation;

$e_{r} = {{e_{r}^{\prime} - {j\; e_{r}^{''}}} = {e_{r}^{\prime} - {j\left( {e_{r\; d}^{''} + \frac{\sigma}{\omega \; e_{0}}} \right)}}}$

where, e_(r)=relative permittivity e_(r)′=real part of relative permittivity e_(r)″=imaginary part of relative permittivity e_(rd)″=dielectic losses σ=conductivity losses ω=frequency e₀=permittivity in a vacuum

As frequency ω increases in the denominator of the equation, the conductivity losses diminish. “In earlier literature, common practice was to convert the whole measured loss into a conductivity term. It was justified when only low frequencies were used, where the loss by conductivity dominated, but otherwise this approach would yield a nonphysical interpretation (Nyfors and Vainikainen, 1989).” Understanding the importance of dielectric losses or the ability to efficiently couple power into geologic formations, especially connate water that is ubiquitous in the subsurface, is fundamental to the HPM System. Initial research by this Inventor focused on determining conductivity versus dielectric losses as a function of frequency. A special resonant cavity was designed to measure permittivity of geologic samples using a vector network analyzer. Numerous permittivity tests were conducted using common geologic materials with varying moisture and organic compound contents. Results of the permittivity measurements confirmed the above equation showing that conductivity losses dissipate at frequencies in the gigahertz range where dielectric losses dominate. Coupling energy into the geologic formation to dielectrically heat geologic formations is efficient and forms the basis of the HPM system.

The technical literature is inconsistent but the term microwave can cover the frequency spectrum from 300 MHz to 300 GHz and includes the physical processes of conductive and dielectric losses. At frequencies below 1 gigahertz, ions in the groundwater act as a charge carrier and e_(r)″ is dominated by the influence of ion conductivity. Once subsurface temperatures reach the boiling point, the water evaporates and the charge pathway is lost. Power is only supplied to the electrode that increases in temperature and now heats by thermal conduction. Initially, proponents of low frequency heating used the term electrodes until the term was later replaced by heaters. Low frequency heating tries to heat the rock which is an insulator by thermal conduction—a highly inefficient method. Conversely, at frequencies greater than 1 gigahertz, substances such as water exhibit strong orientation polarization and absorb energy. Once water and oil are removed, the remaining rock exhibits low losses so the microwave field can penetrate deeper into the rock. This phenomenon is referred to as a migrating phase boundary.

The Inventor had noted during an experiment concerning the removal of contaminates from soil that there was a variation in permeability of the soil and in the viscosity of the contaminants. A full scale high power microwave (HPM) system, consisting of a klystron, circulator, dummy load, antenna coupled to the klystron through the circulator, power supply and wiring and cooling system, had been assembled to propagate microwave energy into a container holding contaminated soil through a phased array antenna surrounded by the soil. This work by the Inventor was done in collaboration with Dr. Donald Ensley, who had become the Inventors mentor in the field of microwaves.

Dr. Ensley filed a patent application discussing the scientific principles of this work and the application issued as U.S. Pat. No. 5,299,887 on Apr. 4, 1994. This U.S. Pat. No. 5,299,887 is incorporated herein by this reference as though set forth in full.

It later occurred to the Inventor, after observing the action of the microwave energy in the test soils, that the scientific principles at work in this experiment had possible applications to the extraction of oil from kerogen in oil shale and the extraction of oil from oil (tar) sands.

Upon this realization of the possible applicability and the belief of the applicability to oil shale and oil sands, the Inventor herein filed a patent application in his name and the name of Dr. Ensley (although deceased). The '057 patent issued from this application on Nov. 9, 2010.

Kiamanesh (U.S. Pat. No. 5,082,054) describes the correct frequency to achieve dielectric heating but the operational protocol fails to develop a migrating phase boundary. Using the term microwave flooding, Kiamanesh describes the drainage of water to a series of canals or wells where liquid water from the rock is collected. The operational protocol in the patent calls for the selective tuning of frequency to develop a plasma torch that creates a source of energy in the subsurface and dominates subsurface heating. Conversely, the method described in the '057 patent and applied in the inventions disclosed in this application for creating microwave induced permeability uses sufficient power to rapidly heat the formational water to a vapor phase that rapidly expands in the rock creating interconnected porosity and fracture permeability. Since the bulk of the power couples into the water and creates steam that egresses toward the well containing the antenna and then strips the oil or kerogen from the rock in the near field. Studies have shown that the background permittivity of most rock is sufficiently low enough to allow penetration rates of 25 meters once the lossy water and hydrocarbon material have been removed. The high power microwave system relies on rapid dielectric heating and not the questionable ability to create plasma torches as described by Kiamanesh.

A critical environmental advantage of the microwave system is the availability of water. Most hydrocarbon reservoirs contain varying amounts of water that efficiently interact with a microwave field. The rapid heating and rapid expansion of in situ water by microwave heating fractures the rock creating pathways for oil to flow to the production wells. Unlike hydrofracking that requires large amounts of water and the disposal of contaminated water, the microwave can fracture the rock using the in-situ water. Based on available moisture data, approximately 1 barrel of water will be produced with every 2 barrels of oil. For semi-arid regions of the world, this additional water would be a valuable benefit created during microwave oil production. Universally, however, and more importantly is the fact that the Qmast microwave system when compared to hydrofracking requires no additional water resulting in the conservation of millions of gallons of water for each and every well drilled.

Studies indicate that the HPM system and method of use can liquefy or vaporize the kerogen and create pathways for the fluid oil migration up to a radius of 25 meters from the antenna. The direction of radiation from the antenna will be rotated in segments until the oil has been removed from a complete circle. The antenna is then moved up in the well and the process is repeated. Quality grade oil shale can range up to 300 meters in thickness permitting a large cylinder to be exposed to the microwave energy in a single well. As a consequence, the possible production from this well may be calculated, which emphasizes the potential of the HPM system and the method of use. It has been reported that the concentration of kerogen per ton of oil shale in the Colorado oil shale field ranges from 20 to 80 gallons per ton. Based on conservative assumptions, the HPM system with an antenna 1 meter in length and the ability to radiate out from the antenna 10 meters in an area having a concentration of 60 gallons of oil per ton of rock and a thickness of 100 meters, will produce over 128,500 barrels of oil. Using a price of approximately $50.00 per barrel, the value of the oil recovered by use of the system at this single well will be approximately $6,425,000.

Production estimates are based solely on the amount of energy required to raise the kerogen to pyrolysis temperature based on the rock's specific heat capacity. However, the system has the capability to create superheated fluids that can strip kerogen from the rock and greatly enhance removal efficiencies.

Increasing Formational Pressures

Another common oil field practice is to inject water to increase formational pressures in existing oil fields to increase oil production. In semi-arid regions such as Texas or the arid Middle East, the availability of water is an issue. Following the teachings of Billman (U.S. Pat. No. 8,672,027), by increasing the temperature of the matrix material, fluid expansion will occur with a subsequent increase in internal pore pressure. Increasing the internal pressure of the pores within the matrix allows the liquid hydrocarbons to move through the pores and into the fractures where it can be collected. Billman relies on conductive heating methods that have limited range and the inability to induce additional fracturing. A dedicated high power microwave system could be used to the increase formational pressure more efficiently and over a larger area than simple conductive heating. Excess natural gas from the oil field can power the microwave system.

SUMMARY OF INVENTION

To further enhance the extraction of oil from shale, sands and exhausted wells, the method of creating microwave induced permeable zones (MIPZ) with the addition of circulation is employed. A further improvement is the interconnection of microwave induced permeability zones (MIPZ). The MIPZ concept allows for the circulation of fluids in the subsurface to enhance hydrocarbon production.

As taught in the '057 patent, a field portable microwave system may be deployed to fracture and increase primary permeability of the rock around the hydrocarbons, thereby providing an egress pathway for fluids (including the oil) created by the reduction in viscosity by microwave heating. The effectiveness of in-situ technologies to treat or remove organic materials from porous media is controlled by the permittivity and permeability of the producing formation. Permittivity allows energy to couple into water and hydrocarbons and once these compounds are removed, the reduction in permittivity allows for migrating phase boundaries to reach greater distances into the subsurface. Laboratory testing using resonant cavities measured the background rock permittivity indicating depths of penetration up to 25 meters are possible for microwave frequencies above 2 GHz. This penetration depth makes it possible to separate circulation wells by distances of up to 50 meters.

Variations in permeability control the rate and direction that fluids migrate in the subsurface. Providing permeable pathways in the subsurface not only allows fluids to escape but provides pathways for the addition of solvents and catalysts to significantly increase oil production efficiencies and rates. Connecting these pathways where solvents and catalysts can be circulated under controlled temperature and pressure conditions presents the potential to not only increase production but the ability for on-site fluid separation. Energy is conserved during the production of hydrocarbons, clean water is produced that offsets oil production demands, and subsurface reservoirs are created for carbon sequestering.

The creation of MIPZ zones and the circulation of fluids will greatly enhance the extraction of oil from shale and sand and other geologic materials. A major need in the oil industry is the ability to rehabilitate conventional oil wells. Reduction in permeability in the region surrounding the well is due to the deposition of paraffin, other similar high viscosity materials, or formational damage. Existing technologies such as heated oil or acidation are limited due to the lack of permeability in the producing formation immediately surrounding the well. Operators can increase pressure to force the hot oil or acid into the formation but this commonly leads to preferential flow zones that absorb the majority of fluids while leaving large portions of the rock formation near the well unaffected.

The microwave approach to rehabilitating conventional wells relies on the basic principle of continuity as described in Uren (1935) that compares the increase in drainage areas for a 6-inch well and a 60-inch well. The increase in drainage area for a 60-inch well compared to a 6-inch well results in formational pressure drops that will double production in rehabilitated wells. The combination of interconnection of primary porosity and fracturing of the rock by microwave radiation can create a cylindrical MIPZ surrounding the well that hydrodynamically behaves as a 60-inch well.

While efficient production of hydrocarbons is possible by the direct application of microwave energy in the subsurface, the HPM microwave system can be used to rehabilitate conventional wells known as stripper wells where production has decreased over time due to the clogging of the formation in the vicinity of the well. By replacing the steel production casing with low-loss dielectric casing, microwave energy can be radiated from the wells to create a permeable region that acts as a large diameter well increasing the drainage area and subsequent hydrocarbon production.

Older conventional wells commonly have production strings with a 5-inch ID working area. An in-situ microwave hydrocarbon production system presented by Kearl (Pub. No: US2013/023637) is intended for larger diameter wells (9-inch or greater). For well rehabilitation, a 4.5-inch OD subsurface microwave system is proposed to rehabilitate wells. Moderate power microwave systems are capable of removing well-clogging materials in conventional oil wells and create a MIPZ surrounding the well to increase future production by conventional production methods. Modification in the design of the in-situ HPM system to included smaller diameter and lower power are presented as an extension of the technology for well rehabilitation applications.

Another important application of the HPM system is to increase formational pressure in existing oil fields. Following the teachings of Billman (U.S. Pat. No. 8,672,027), by increasing the temperature of the matrix material fluid expansion will occur and subsequent increase in internal pore pressure. Increasing the internal pressure of the pores within the matrix allows the liquid hydrocarbons to move through the pores and into the fractures where it can be collected. Billman relies on conductive heating methods that have limited range and ability to induce additional fracturing. A dedicated high power microwave system could be used to the increase formational pressure more efficiently and over a larger area than simple conductive heating.

Creating interconnected MIPZ zones between wells for subsurface oil recovery circulation systems, an on-site process facility to separate fluids, capture carbon dioxide for oil recovery or sequestration, are natural extensions of the microwave system. Carbon dioxide is commonly used in the oil field for secondary oil recovery systems. Supercritical fluids can be circulated in the subsurface to take advantages of the permeability of a gas and the solvent ability of a liquid. Significant reductions in emissions during hydrocarbon production can be significantly reduced by the capture and the sequestering of climate warming gases in subsurface cavities created during subsurface extraction of oil and gas.

Once hydrocarbon production declines to uneconomic levels, CO₂ can be injected under high pressure into the porous cavities created by microwave heating for carbon sequestration. For areas covered by the Green River Formation, nearby limestone deposits make it possible to produce cement while at the same time sequestering the CO₂ from cement production. It is estimated that 6 percent of man-made sources of greenhouse gases comes from the production of cement.

Modifications to the proposed HPM systems include directional couplers to measure reflected power and a feedback control circuit that adjusts the klystron tube to remain on antenna cavity resonance during thermal expansion or load variations. Conventional coupler located between the iris plate of the antenna and the circulator can measure direct or reflected power and this information used to maintain cavity resonance or quantify the properties of the load or rock including changes in permittivity, water content, and phase boundaries.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating the circulation concept for the extraction of hydrocarbons.

FIG. 2 is a schematic diagram illustrating a three well circulation system where microwave induced permeable zones are in place in the lower regions of each well.

FIG. 3 is a top schematic view of a microwave production field utilizing numerous well in a convention 5-spot wells spacing.

FIG. 4 is a schematic and block diagram of a horizontal circulation well pair.

FIG. 5 is a schematic diagram showing the offset of the antenna relative to the borehole.

FIG. 6 is a schematic diagram showing the downhole tool of FIG. 5 in use.

DETAILED DESCRIPTION

FIG. 1 shows the application of the HPM system with circulation between two wells drilled a proper distance 35 apart to provide for intersecting or overlapping induced permeability zones. Alternatively, rehabilitation may be involved and the two wells may be one exhausted well and one drilled a proper distance 35 from the old well or both wells may be old wells spaced the proper distance 35 apart for the permeability zones to intersect or overlap. In all cases, the combination of the creation of the microwave induced permeability zones (MIPZs) and circulation of selected fluids between the wells will increase the production of oil from the wells and the created MIPZs. It is projected that the HPM system will have a penetration depth in oil shale which makes it possible to separate wells by a distance 35 of up to 50 meters or more for extraction of oil from shale. The shape of the MIPZs created by the gain and directivity of the antenna are not exact but a representation of antenna patterns from the literature. It is possible to create different MIPZs shapes and dimensions depending upon the application.

FIG. 1 shows a HPM field system 1 at a first well 2. This same system 1 may have been used at well 36 to create MIPZ 38 radiating from well 32 toward well 2. Alternatively, a separate HPM system 40 may be located at well 32. The high gain directional antenna 9 of the HPM system 1 creates a permeable pathway 3 from well 2 that connects with the MIPZ 38 from well 32 at the mid-way point 28 between the wells. This provides a permeable path 3 and 38 for the circulation (represented by the arrows 39) of superheated or supercritical fluids, catalytic agents, hydrogen, or other compounds to aid in the stripping and removal of kerogen, bitumen, and other hydrocarbon deposits from the subsurface areas 4 and 41 adjacent to the permeable pathways 3 and 38, respectively. Interconnected permeable zones 3 and 38 are created by microwave beams from each well that intersect at the mid-way point 37 between the wells. Fluids, including but not limited to supercritical, superheated, or various catalysts, are circulated between the wells 2 and 36 via a compressor or pump (not shown) inside the processing unit 7 to reduce the viscosity of oil in areas 4 and 41 adjacent to microwave induced permeable zones 3 and 38. Liquid product flows towards the wells where it is recovered by well pumps 6 and 42. The processing unit 7 is capable of, but not limited to, gas separation, distillation, heat recovery and addition of fluids to enhance the hydrocarbon removal efficiencies. For microwave distillation, the hydrocarbon fluid is already heated thereby reducing energy cost for refining petroleum products.

Side lobes 5 are created by the radiating pattern of the antenna. Submersible pumps 6 in the well 2 removes liquid hydrocarbons and discharges them at the surface at the outlet of pipe 8 to storage tanks or processing facilities (not shown). Similarly, the liquid hydrocarbons from well 32 are pumped by pump 42 to the surface and are discharged at the outlet of pipe 43. The surface processing unit 7 contains circulation pumps, separation units, compressors, injection units, instrumentation systems, co-generation units, and steam or supercritical fluid generators. The circulation pump in processing unit 7 takes off gases from well 32, adds other fluids and then injects them into well 2 to create a circulation system between the two wells. Off gases may be recirculated several times to assist in hydrocarbon removal. Separation units can consist of, but not limited to, gas separation units to provide fuel to run power generation units and both in-situ and ex-situ separation of petroleum compounds into useful products such as propane, jet fuel, diesel fuel and gasoline.

Compressors may be used to generate additional supercritical fluids that, if necessary, can supplement those created in-situ by microwave heating and pressure control. Injection units may be used for catalysts to be added to improve hydrocarbon removal efficiencies by reducing the activation energy required to liquefy or vaporize hydrocarbons. Instrumentation systems monitor, but not limited to, temperature, pressure, mass flow rates, and gas concentrations. This data is linked to the computer control system (not shown) for the High Power Microwave system. Data linked to verified physical computer codes will guide the HPM system operators. Steam generators and co-generation power units are possible additions to the processing unit 7.

A fundamental system employing the concept of using a HPM system and circulation of fluids has been shown in FIG. 1. The extraction of hydrocarbons may be further increased by rotating the antenna of the HPM system to cover a circle rather than just the segment of the MIPZ. Additionally, the antenna may be raised a selected distance, such as the length of the antenna, to create MIPZ above existing MIPZ. This would be done in both wells to have intersecting or overlapping MIPZ. The antennas may then be rotated to cover a circle and to create a cylinder with the oil removed to provide a larger reservoir for sequestration.

Operation methodologies can be broadly divided into hydrocarbon production for two or more interconnected wells and well rehabilitation. Operation production methodologies include selecting the correct well design (i.e., diameter, orientation, multiple wells), creation of interconnected high permeability zones between wells that allows for the circulation of superheated or supercritical fluids or hydrocarbon stripping catalysts. Subsurface operational methodologies include different antennas with varying gain and directivity to create permeable pathways to surrounding wells, producing natural gas to power the HPM systems reducing power requirements, and in-situ and above ground fluid separation and distillation to create specific hydrocarbon fuels on site.

Well rehabilitation methodologies are focused on, but not limited to, conventional wells where production rates have declined due to permeability decreases in the vicinity of the well resulting from the buildup of paraffins and other high viscosity petroleum components. HPM system modifications include a lower power HPM downhole system capable of use in 5-inch diameter wells to depths of several kilometers. Antenna designs for varying frequency, gain, and directivity for use in either production or rehabilitation of wells may include an offset of the antenna relative to the well, as shown in FIG. 5, allowing sufficient distance between the antenna output and the lossy material relative to the frequency. Advances in low loss materials such as permeable ceramic and fiberglass well casings, and installation techniques in existing steel cased wells using downhole milling tools and low loss production sleeves allow the efficient propagation of microwave energy from the well to the formation.

During operation, the antenna is subject to thermal expansion. A feedback control loop (not shown) is used to tune the klystron in order to maintain antenna cavity resonance when temperature changes occur. Arc detectors using, but not limited to, crow bar systems to protect the klystron tube is another HPM system modification. Directional couplers may be used to measure transmitted and reflected power and quantify permittivity, water content, and phase boundary changes in rock being heating by microwave power.

The environmental goal of the HPM system is zero emissions during the production of hydrocarbons. Subsurface permeable zones created by the HPM system can be used as sequestering reservoirs. Other environmental benefits include on-site distillation that reduces power requirements for refining facilities, using a portion of the hydrocarbon production to power the generators for the HPM system thus reducing outside power sources, and carbon sequestering of not only production emissions but a reservoir for other carbon emission producers.

FIG. 2 illustrates the operation of the HPM system generally for, but not limited to, shallow systems accessed by vertical wells 2, 36 and 44. The base of the hydrocarbon zone penetrated by the wells is first microwaved to provide permeable pathways 45 and 46 for the collection of liquid product. The antenna 9 is placed just above the initial radiated permeable zones 45 and 46 where the radiation patterns overlap at point 47. The antenna 9 can be moved up in the well to launch a migrating phase boundary that heats kerogen or bitumen and decrease the viscosity allowing liquids to flow under gravity into lower MIPZs where a permeable pathway exists to the collection wells 2 and 36. A migrating phase boundary 14 is launched that dielectrically heats water, kerogen or bitumen and reduces their viscosity. Liquid products migrate downward to the permeable zones 45 and 46 and out to the wells 2 and 36 for collection by pumps 6 and 50, discharged into pipes 8 and 51, and collected in surface storage tanks 10 and 52.

Another application for the microwave circulation concept uses a five-point pattern where multiple wells can be interconnected (FIG. 3). Using the numbers of FIG. 1, interconnected permeable zones 3 between the wells 2 allow for circulation of production enhancing fluids that interact with edges 4 of the microwave induced permeability zones 3. Oil is collected at wells 49. Multiple wells may be used for injection and removal of circulation fluids. A single injection well services several adjacent extraction wells for a large volume recirculation hydrocarbon production system.

FIG. 4 shows an application of the HPM system and circulation method for horizontal well pairs 11 and 12 where an antenna 23 is lowered to the end of well 11 and radiates microwave power to create a microwave induced permeable zone 3 between the wells 11 and 12. The antenna 23 and the above ground equipment 55 are consistent with designs presented in patent application US 2013/0213637. The antenna is repositioned at a selected distance from the end of the well and the process is repeated. At the same time, oil production enhancing fluids are circulated between the horizontal wells while oil is collected in the lower well and pumped by pump 6 to the surface. This process is repeated along the length of the horizontal wells 11 and 12.

FIG. 5 illustrates the concept of an in-situ microwave rehabilitation system in a well 24 that uses, but not limited to, frequencies in the C-band to X-band, with a Sheet-beam or Multi-beam klystron 18 with a production casing replaced with low-loss porous ceramic, fiberglass or other low-loss casing 25. The antenna 23 is offset to increase the distance from the antenna to the load to reduce VSWR. A directional coupler (not shown) measures reflected power and links to a feedback control circuit than tunes the klystron to remain essentially on antenna cavity resonance when subjected to thermal expansion effects or load variations.

Well rehabilitation of conventional wells commonly 5 inches in diameter and 1000 meters in depth requires significant modifications (FIG. 5). Reduction in power in the 100 to 250 KW range is required. Downhole steel production casing is replaced by a specially designed low-loss permeable ceramic casing sleeve 24 that allows the propagation of microwaves into the subsurface and the collection of hydrocarbons in the well. One approach for rehabilitating the well is creating a high permeable cylinder surrounding the small diameter well that would mimic a large diameter well. Uren (1935) demonstrated that increasing the well diameter from 6″ to 60″ doubles production rates. The microwave system can create subsurface permeable cylinders that exceed 10 meters radial distance from the well and hydrodynamically behave as a well bore. The article states that the reduction in the pressure gradient due t the increase in surface area of the well diameter will result in doubling production.

FIG. 6 illustrates several modifications for the downhole HPM system. Microwave beams can be directed toward existing faults 28 and micro-fractures 31 and using a subsurface or surface packer 29 with a pressure relief valve 30, downhole pressures can be controlled to several thousand pounds per square inch. This is the application of a downhole HPM system for increasing formational pressures in existing oil fields. The insert in the figure shows the expansion of micro-fractures 31 due to the increased pressure by microwave heating. The downhole microwave system 33, consistent with FIG. 5, would be placed in the well and using a high gain directed beam, to create permeable pathways (MIPZs) between the well and permeable features such as faults and fractures. The pressure downhole can be controlled by the amount of power radiated by the microwave system and flow control values (not shown) on the surface. Due to the ability to radiate out to distances of up to 25 meters, a large area of the formation can be pressurized.

In multiple well fields where the one or more HPM systems are operating, formational pressure will be increased that will assist in hydrocarbon removal for all of wells in the field. This same idea can be applied to existing well fields where a specifically design well could be drilled and installed with a dedicated HPM system whose function is to increase temperature and pressure in the formation in order to increase hydrocarbon production from existing wells. As taught in the '057 patent, it is possible to control downhole temperature and pressure. Based on geologic knowledge, permeable zones can be radiated from the well to intersect existing fractures and faults, increase the pressure and temperature to increase aperture the fractures thus increasing the radius of influence, and driving hydrocarbons from tight rock matrixes into the fractures for collection at existing production wells.

The goal of this technology is zero emissions for the production of hydrocarbons. The ability to sequester all hydrocarbon production emissions in abandoned subsurface permeable regions plus provide storage sites for other sources of greenhouse gases makes the technology environmentally friendly. The HPM system is an environmentally sound method to produce hydrocarbons in numerous regions in the country and the world but especially in arid regions where water is a limited resource. Depending on the number of production wells, moderate quantities of water could be produced to supply operational and reclamation needs. Self-contained units can be deployed to remote locations to provide self-contained fuel stations.

While the description above contains specificity, this should not be construed as limiting the scope of the invention; but merely as providing illustrations of the presently preferred embodiment of the invention. Although preferred embodiments and method for extracting subsurface hydrocarbons have been described above, the inventions are not limited to the specific embodiments, but rather the scope of the inventions are to be determined as claimed. 

What is claimed is:
 1. A method of increasing the extraction of hydrocarbons between two or more wells comprising the steps of creating a permeable pathway between selected wells and circulating fluids through the wells across the pathways.
 2. The method in accordance to claim 1, wherein the creation of permeable pathways uses gain and directivity of the antenna to efficiently create microwave induced permeability zones (MIPZs) used in the circulation process.
 3. The method in accordance to claim 1, wherein the circulating fluids through the wells are heated and pressurized to efficiently strip hydrocarbon deposits.
 4. The method in accordance to claim 1, wherein the permeable pathways are created by an HPM system that includes a directional coupler to measure reflected power and links to a feedback control circuit that tunes the klystron to remain essentially on antenna cavity resonance when subjected to thermal expansion effects or load variations.
 5. The method in accordance with claim 4 wherein the directional coupler measures transmitted and reflected power and/or quantifies permittivity, water content, and phase boundary changes that occur in geologic formations during microwave heating.
 6. The method in accordance to claim 1, wherein the pressure and temperature are controlled for on-site gas separation and distillation of hydrocarbon products.
 7. A method to rehabilitate conventional low volume stripper wells by applying high power, high frequency microwave energy to remove high viscosity compounds that clogs the formation and creating a high permeable region surrounding the interior of the well that mimics large diameter wells increasing drainage areas and conventional oil production rates.
 8. The method in accordance to claim 7, wherein an in-situ HPM system capable of reaching depths on the order of 1 kilometer or greater is employed.
 9. The method in accordance to claim 7, wherein low-loss permeable casings such as ceramic, fused quartz or fiberglass replace the production string allowing efficient microwave propagation into the rock formation and increasing drainage areas.
 10. The method in accordance to claim 7, wherein the microwave energy is applied by an antenna that is offset to increase the distance from the antenna slots to the load in order to reduce VSWR.
 11. A method that produces pore and bound water that is not hydraulically connected to existing water rights.
 12. A method to selectively target existing subsurface permeable zones, increase the formational pressure over a large radial distance from the well with an installed microwave system and increase hydrocarbon production from existing wells.
 13. A method that produces porous subsurface cavities capable of efficient CO₂ sequestration.
 14. The method in accordance in claim 13 uses local limestone resources to produce cement and sequester CO₂ in microwave created cavities 